The present invention relates to utility meters, such as water meters or meters for gas or electric service. The invention more particularly relates to a transducer for converting mechanical movements, such as revolutions of a metering element to electrical pulses which can be conditioned to become digital signals.
An example of a prior metering pulse generator is illustrated and described in Strobel et al., U.S. Pat. No. 4,868,566, issued Sep. 19, 1989, and assigned to the assignee of the present invention. A piezoelectric material is arranged as a thin, elongated layer on a cantilevered spring member. A tooth on a rotating sprocket contacts an extended end of the spring member to produce a bending movement, which is then followed by a rapid return movement. This generates a pulse signal which is amplified by an amplifier positioned on the spring member.
In this prior construction, the spring member provided a load on the torque of the meter mechanism. This can have an effect on accuracy of the meter at the low end of the flow measurement range. It would be desirable to reduce such torque loads as much as possible. While technologies such as optics eliminate mechanical loading, they introduce new issues such as batteries and other electrical power sources.
There are also known in the art of flow meters generally, a type of pulse generator utilizing magnetically switchable elements. Examples of such pulse generators are shown and described in Onoda et al., U.S. Pat. No. 4,265,127; Bohm et al., U.S. Pat. No. 4,579,008; Jerger et al., U.S. Pat. No. 4,793,192; Merriam, U.S. Pat. No. 5,311,581 and British Patent Specification GB2102129A. Many of these utilize magnetically switchable elements, and a basic pulse generator is disclosed in U.S. Pat. No. 3,780,313.
The prior art does not provide a suitable metering pulse transducer for producing pulses that can be conveniently digitized and transmitted in networks for the collection of metering data. Such transducers should be compact and lightweight, and the prior art devices are not suitable in this respect, because they do not most efficiently utilize the principles of generating and sensing signals using the switchable magnetic elements. Such devices should be easy to manufacture and low in cost, and many of the prior art devices are too expensive to manufacture or not sufficiently desirable for utility metering applications intended for the present invention.
The invention is embodied in a pulse transducer, which utilizes a compact rotor for carrying a plurality of magnetically switchable elements, and two magnets positioned adjacent the rotor for switching each element four times to produce two pulses in one revolution of a rotor. A compact and efficient sensor is provided for sensing pulses generated by the switching of the magnetically switchable elements as they are moved into and out of the magnetic fields of the two magnets.
The rotor assembly of the present invention provides very little drag and consumes very little torque in mechanical drive mechanisms. The rotor can be used to directly drive a least significant digit analog meter dial, or it may be connected to a meter register drive train to provide digitized electrical signals at the same time as mechanical meter movements are transmitted to a mechanical odometer or a mechanical register dial. The invention can also be embodied in a turbine-type flow meter, and other embodiments.
As compared with the prior art relating to switchable magnetic elements, the present invention is an improvement over devices which include only a single switchable magnetic element, or a magnetic pickup associated with only a single magnetic element. The prior art does not utilize two magnets to produce a switching of each magnetic element four times to produce two pulses in one revolution of a rotor.
The present invention also effectively uses one sensor coil in association with the two magnets and a plurality of switchable magnetic elements in a compact arrangement.
In a preferred embodiment of the invention, the number of switchable magnetic elements is five, so that ten electrical pulses are produced for each revolution of the rotor. This corresponds to a decimal number readout device.
The prior art devices do not generate ten pulses per revolution of a rotor carrying the magnetic elements. Indeed, in many prior art devices, the magnets may be moved instead of the switchable elements. Unless ten pulses are produced per cycle or revolution, mechanical or electrical conversion is required to produce a decimal pulse count.
The invention provides a more compact device than the prior art, making it suitable for use in meter registers which are relatively small instruments.
The invention is disclosed in terms of meter registers for use in measuring water consumption, but may also find application in the metering of utilities such as gas or electricity, and or in other types instrumentation in which it is desired to convert mechanical movement to electrical pulses.
Other objects and advantages will be apparent to those of ordinary skill in the art from the description of the preferred embodiments which follow. In the description, reference is made to the accompanying drawings, which form a part hereof, and which illustrate examples of the invention. Such examples, however, are not exhaustive of the various embodiments of the invention, and therefore, reference is made to the claims which follow the description for determining the scope of the invention.